Coating manufacturers have achieved significant progress in developing novel components for polyurethanes to improve coating properties, although less effort has been put into the search for novel catalyst systems. The usual catalysts for this process are dibutyltindilaurate and tertiary amines. Dialkyl and trialkyltin derivatives, classes of the compounds to which dibutyltindilaurate belongs to, have been discussed as having some issues regarding human toxicity. See, for example, Boyer, I. J., Toxicology, 1989, 55, 253 and Lytle, T. F.; Manning, C. S.; Walker, W. W.; Lytle, J. S.; Page, D. S., Appl. Organomet. Chem., 2003, 17, 653. Divalent tin compounds as disclosed herein, which do not have alkyl-tin bonds, have been tested as catalysts for polyurethane formation.
Organometallics of the group 14 elements, particularly dibutyltin derivatives, are known to catalyze transesterification, transcarbamoylation and urethane formation. While there has been progress in developing novel components for polyurethanes to improve coating properties, a need remains for novel catalyst systems. Known catalysts for forming polyurethanes include dibutyltindilaurate and tertiary amines. Dialkyl and trialkyltin derivatives, classes of the compounds to which dibutyltindilaurate belongs, have some toxicity to humans, so less toxic catalysts are desired.
Jousseaume, B. et al., (“Air Activated Organotin Catalysts for Silicone Curing and Polyurethane Preparation” (1994) Organometallics 13:1034), and Bernard, J. M. et al. (U.S. Pat. No. 6,187,711) describe the use of distannanes as latent catalysts, e.g. Bu2(AcO)SnSn(OAc)Bu2.
B. Cetinkaya, et al., J. Am. Chem. Soc. (1980), 102(6), 2088-9, disclose bivalent germanium, tin, and lead 2,6-di-tert-butylphenoxides and the crystal and molecular structures of M(OC6H2Me-4-But2-2,6)2, where M is Ge or Sn.
Co-pending and co-owned U.S. patent applications (Ser. No. 11/407,003, issued as U.S. Pat. No. 7,625,992 Ser. No. 11/406,994, issued as U.S. Pat. No. 7,626,049, Ser. No. 11/407,009, issued as U.S. Pat. No. 7,371 ,879), all incorporated by reference in their entirety, disclose divalent and quadrivalent tin and germanium compounds and their use as catalysts. (Ser. No. 11/407,003, issued as U.S. Pat. No. 7,625,992) describe quadrivalent derivatives of tin and germanium and their use as catalysts. (Ser. No. 11/406,994, issued as U.S. Pat. No. 7,626,049) describes divalent tin and germanium compounds stabilized by bulky chelating P^O ligands.